This invention relates generally to the disposal and treatment of hazardous waste and more specifically to the treatment of biologically hazardous waste.
Although this invention has tremendous applications to a variety of items to be cleaned including but not limited to, dental tools, surgical instruments, implants, etc., for an understanding of the problems associated with cleansing and sterilization, the following discussion focusses on the cleansing and sterilization of contact lenses.
The success or tragic failure of contact lens wear is ultimately determined by the care and aseptic handling of the lenses. With over seventeen million contact lens wearers in the United States spending two billion dollars on contact lens supplies, a simple one step cleaning and sterilizing process is sought. Both hard and soft lenses currently need daily, or in the case of extended wear contacts, weekly cleaning and antiseptic treatment.
By their very nature, being in close relationship with the wearer for extended periods of time, contact lenses are susceptible to both: buildups of protein and lipids from the wearer; and also from contamination from microorganisms. Either of these, buildup or contamination, can have debilitating affects such as reduced vision, scarring of the eye, and even blindness.
Hydrophilic contact lenses, being soft and composed mainly of water, have made the problem of cleaning even more difficult. Physical pressure on the hydrophilic lense may cause rips; strong disinfectants become lodged within the body of hydrophilic lense itself and then irritate the wearer's eye causing an ulcer.
Without a good cleaning process, both the hard and soft contact lense is susceptible to a wide variety of contaminating microorganisms including: Acanthamoeba, Pseudomonas organisms, Alcaligenes faecalis, staph, Aureus, and Enterobacter aerogenes.
For a through understanding of the diseases associated with contact lenses, see: "Pseudomonas aeruginosa Contamination of Hydrophilic Contact Lenses and Solutions", by Milauskas, appearing in Transactions of the American Academy of Ophthalmology and Otology, vol. 76, Mar.-Apr. 1972, page 511; "Complications Associated with Contact Lens Solutions", by Morgan, appearing in Ophthalmology AAO, vol. 86, Jun. 1979, page 1107; "The Soft Plastic Contact Lenses", by Dastoor, appearing the Indian Journal of Ophthalmology, vol. XXI, on page 25; "Microbiological Evaluation of Soft Contact Lens Disinfecting Solutions" by Houlsby et al., appearing in the Journal of the American Optometric Association, vol. 55, No. 3, page 205; and, "Susceptibility of Acanthamoeba to Soft Contact Lense Disinfection Systems", appearing in the Investigative Ophthalmology & Visual Science, Apr. 1986, Vol. 27, page 626.
Additionally, the high water content of hydrophilic contact lenses make them more susceptible to the formation of "jelly bump" deposits which are composed primarily of lipids and calcium. These lipid formations are usually long and intermediate chain cholesterol esters and triglycerides which are particularly difficult to remove from a soft lense without damaging the lense. A good review of this problem is "Origin and Composition of Lipid Deposits on Soft Contact Lenses" by Hart et al., and appearing in Ophthalmology, Apr. 1986, vol. 93, No. 4, page 495.
The typical method of cleaning, using a saline solution and distilled water approach has not been totally satisfactory. It has been found that this approach does not truly address the contamination problem; indeed, several of the contaminating microorganisms actually thrive in the cleaning environments.
Because of this, the industry has been seeking alternative cleaning approaches which may be used by the wearer, not a laboratory.
One technique proposed is the use of a 3% hydrogen peroxide solution for the cleaning and disinfecting the lenses. The reason for this popularity is that after disinfecting, the hydrogen peroxide is converted into innocuous by-products which are compatible with ocular physiology.
The hydrogen peroxide approach is well described in: "A Comparison of New Hydrogen Peroxide Disinfection Systems" by Krezanoski et al., and appearing in the Journal of the American Optometric Association, vol, 59, No. 3, page 193; "Efficacy of Hydrogen Peroxide Disinfection Systems for soft Contact Lenses Contaminated with Fungi", by Penley et al., and appearing in the CLAO Journal, Jan. 1985, vol. 11, no. 1, page 65; "Reaction to Hydrogen Peroxide in a Contact-Lens Wearer", by Knopf, appearing the American Journal of Ophthalmology, Jun., 1984, page 796; "Hydrogen Peroxide in Anterior Segment [Physiology: A Literature Review", by Chalmers, appearing in Optometry & Vision Science, page 796; and, "Hydrogen Peroxide Sterilization of Hydrophilic Contact Lenses', by Gasset et al., and appearing in Arch. Ophthalmology, vol, 93, Jun. 1975, page 412.
Unfortunately, hydrogen peroxide, at the 3% level or even the 6% level, is incapable of disinfecting some of the hardier microorganisms. Further, hydrogen peroxide does not have noticeable affect upon the "jelly bumps".
Perhaps the most common treatment is the heat method. In this approach the contact lenses are exposed to a temperature of eighty degrees centigrade for a period ten minutes. This approach is more effective than chemicals against microorganisms but the treatment substantially decreases the life of the contact lenses and is usable only with about half of the present contact lenses. Use of this method depends heavily upon the water content and the type of plastic used in the lenses' construction.
Additionally, proteins and other contaminants that are left in the contact lense (buildup) can substantially produce irritation in the eyes of the user.
It is clear from the foregoing that an efficient and through cleaning and sterilizing technique does not exist.